Tuberculosis (TB) is a contagious disease. Like the common cold, it spreads through the air. Only people who are sick with TB in their lungs are infectious. When infectious people cough, sneeze, talk or spit, they propel TB germs, known as bacilli, into the air. A person needs only to inhale a small number of these to be infected.
Left untreated, each person with active TB disease will infect on average between 10 and 15 people every year. But people infected with TB bacilli will not necessarily become sick with the disease. The immune system “walls off” the TB bacilli which, protected by a thick waxy coat, can lie dormant for years. When someone's immune system is weakened, the chances of becoming sick are greater.
Overall, one-third of the world's population is currently infected with the TB bacillus. About 5-10% of people who are infected with TB bacilli (but who are not infected with HIV) become sick or infectious at some time during their life. People with HIV and TB infection are much more likely to develop TB.
WHO estimates that the largest number of new TB cases in 2008 occurred in the South-East Asia Region, which accounted for 35% of incident cases globally. However, the estimated incidence rate in sub-Saharan Africa is nearly twice that of the South-East Asia Region with over 350 cases per 100 000 population.
An estimated 1.7 million people died from TB in 2009. The highest number of deaths was in the Africa Region.
In 2008, the estimated per capita TB incidence was stable or falling in all six WHO regions. However, the slow decline in incidence rates per capita is offset by population growth. Consequently, the number of new cases arising each year is still increasing globally in the WHO regions of Africa, the Eastern Mediterranean and South-East Asia.
The new reports on the incidence, prevalence and mortality from tuberculosis are alarming (Global tuberculosis control 2010, WHO). Accordingly, the prevalence of TB is the lowest in The Americas at 37/100,000 while corresponding prevalence is 63 in Europe, 160 in Western Pacific, 280 in South-East Asia and 450 in Africa. The mortality rates are accordingly, 2.1 in The Americas to 50 in Africa. Africa accounts for almost 30% of all new cases of tuberculosis, The Americas only 2.9% and the highest incidence is found in South-East-Asia which accounts for 35% of new cases.
HIV and TB form a lethal combination, each speeding the other's progress. HIV weakens the immune system. Someone who is HIV-positive and infected with TB bacilli is many times more likely to become sick with TB than someone infected with TB bacilli who is HIV-negative. TB is a leading cause of death among people who are HIV-positive. In Africa, HIV is the single most important factor contributing to the increase in the incidence of TB since 1990.
WHO and its international partners have formed the TB/HIV Working Group, which develops global policy on the control of HIV-related TB and advises on how those fighting against TB and HIV can work together to tackle this lethal combination. The interim policy on collaborative TB/HIV activities describes steps to create mechanisms of collaboration between TB and HIV/AIDS programs, to reduce the burden of TB among people and reducing the burden of HIV among TB patients.
Until 50 years ago, there were no medicines to cure TB. Now, strains that are resistant to a single drug have been documented in every country surveyed; what is more, strains of TB resistant to all major anti-TB drugs have emerged. Drug-resistant TB is caused by inconsistent or partial treatment, when patients do not take all their medicines regularly for the required period because they start to feel better, because doctors and health workers prescribe the wrong treatment regimens, or because the drug supply is unreliable. A particularly dangerous form of drug-resistant TB is multidrug-resistant TB (MDR-TB), which is defined as the disease caused by TB bacilli resistant to at least isoniazid and rifampicin, the two most powerful anti-TB drugs. Rates of MDR-TB are high in some countries, especially in the former Soviet Union, and threaten TB control efforts.
While drug-resistant TB is generally treatable, it requires extensive chemotherapy (up to two years of treatment) with second-line anti-TB drugs which are more costly than first-line drugs, and which produce adverse drug reactions that are more severe, though manageable. Quality assured second-line anti-TB drugs are available at reduced prices for projects approved by the Green Light Committee.
The emergence of extensively drug-resistant (XDR) TB, particularly in settings where many TB patients are also infected with HIV, poses a serious threat to TB control, and confirms the urgent need to strengthen basic TB control and to apply the new WHO guidelines for the programmatic management of drug-resistant TB.
Although over 37 species of mycobacteria have been identified, more than 95% of all human infections are caused by six species of mycobacteria: M. tuberculosis, M. avium intracellulare, M. kansasii, M. fortuitum, M. chelonae, and M. leprae. The most prevalent mycobacterial disease in humans is tuberculosis (TB), which is predominantly caused by mycobacterial species comprising M. tuberculosis, M. bovis, or M. africanum (Merck Manual 1992). Infection is typically initiated by the inhalation of infectious particles, which are able to reach the terminal pathways in lungs. Following engulfment by alveolar macrophages, the bacilli are able to replicate freely, with eventual destruction of the phagocytic cells. A cascade effect ensues wherein destruction of the phagocytic cells causes additional macrophages and lymphocytes to migrate to the site of infection, where they too are ultimately eliminated. The disease is further disseminated during the initial stages by the infected macrophages which travel to local lymph nodes, as well as into the blood stream and other tissues such as the bone marrow, spleen, kidneys, bone and central nervous system. (See Murray et al. Medical Microbiology, The C.V. Mosby Company 219-230 (1990)).
There is still no clear understanding of the factors which contribute to the virulence of mycobacteria. Many investigators have implicated lipids of the cell wall and bacterial surface as contributors to colony morphology and virulence. Evidence suggests that C-mycosides, on the surface of certain mycobacterial cells, are important in facilitating survival of the organism within macrophages. Trehalose 6,6′ dimycolate, a cord factor, has been implicated for other mycobacteria.
The interrelationship of colony morphology and virulence is particularly pronounced in M. avium. M. avium bacilli occur in several distinct colony forms. Bacilli, which grow, as transparent, or rough, colonies on conventional laboratory media are multiplicable within macrophages in tissue culture, are virulent when injected into susceptible mice, and are resistant to antibiotics. Rough or transparent bacilli, which are maintained on laboratory culture media, often spontaneously assume an opaque R colony morphology, at which time they are not multiplicable in macrophages, are avirulent in mice, and are highly susceptible to antibiotics. The differences in colony morphology between the transparent, rough and opaque strains of M. avium are almost certainly due to the presence of a glycolipid coating on the surface of transparent and rough organisms, which acts as a protective capsule. This capsule, or coating, is composed primarily of C-mycosides which apparently shield the virulent M. avium organisms from lysosomal enzymes and antibiotics. By contrast, the non-virulent opaque forms of M. avium have very little C-mycoside on their surface. Both the resistance to antibiotics and the resistance to killing by macrophages have been attributed to the glycolipid barrier on the surface of M. avium. 
Diagnosis of mycobacterial infection is confirmed by the isolation and identification of the pathogen, although conventional diagnosis is based on sputum smears, chest X-ray examination (CXR), and clinical symptoms. Isolation of mycobacteria on a medium takes as long as four to eight weeks. Species identification takes a further two weeks. There are several other techniques for detecting mycobacteria such as the polymerase chain reaction (PCR), mycobacterium tuberculosis direct test, or amplified mycobacterium tuberculosis direct test (MTD), and detection assays that utilize radioactive labels.
One diagnostic test that is widely used for detecting infections caused by M. tuberculosis is the tuberculin skin test. Although numerous versions of the skin test are available, typically one of two preparations of tuberculin antigens are used: old tuberculin (OT), or purified protein derivative (PPD). The antigen preparation is either injected into the skin intradermally, or is topically applied and is then invasively transported into the skin with the use of a multi-prong inoculator (Tine test). Several problems exist with the skin test diagnosis method. For example, the Tine test is not generally recommended because the amount of antigen injected into the intradermal layer cannot be accurately controlled. (See Murray et al. Medical Microbiology, The C.V. Mosby Company 219-230 (1990)).
Although the tuberculin skin tests are widely used, they typically require two to three days to generate results, and many times, the results are inaccurate since false positives are sometimes seen in subjects who have been exposed to mycobacteria, but are healthy. In addition, instances of misdiagnosis are frequent since a positive result is observed not only in active TB patients, but also in persons vaccinated with Bacille Calmette-Guerin (BCG), and those who had been infected with mycobacteria, but have not developed the disease. It is hard therefore, to distinguish active TB patients from the others, such as household TB contacts, by the tuberculin skin test. Additionally, the tuberculin test often produces a cross-reaction in those individuals who were infected with mycobacteria other than M. tuberculosis (MOTT). Therefore, diagnosis using the skin tests currently available is frequently subject to error and inaccuracies.
The standard treatment for tuberculosis caused by drug-sensitive organisms is a six-month regimen consisting of four drugs given for two months, followed by two drugs given for four months. The two most important drugs, given throughout the six-month course of therapy, are isoniazid and rifampin. Although the regimen is relatively simple, its administration is quite complicated. Daily ingestion of eight or nine pills is often required during the first phase of therapy; a daunting and confusing prospect. Even severely ill patients are often symptom free within a few weeks, and nearly all appear to be cured within a few months. If the treatment is not continued to completion, however, the patient may experience a relapse, and the relapse rate for patients who do not continue treatment to completion is high. A variety of forms of patient-centered care are used to promote adherence with therapy. The most effective way of ensuring that patients are taking their medication is to use directly observed therapy, which involves having a member of the health care team observe the patient take each dose of each drug. Directly observed therapy can be provided in the clinic, the patient's residence, or any mutually agreed upon site. Nearly all patients who have tuberculosis caused by drug-sensitive organisms, and who complete therapy will be cured, and the risk of relapse is very low (“Ending Neglect: The Elimination of Tuberculosis in the United States” ed. L. Geiter Committee on the Elimination of Tuberculosis in the United States Division of Health Promotion and Disease Prevention, Institute of Medicine. 2000.)
Needed are effective therapeutic regimens that include improved vaccination and treatment protocols. Currently available therapeutics are no longer consistently effective as a result of the problems with treatment compliance, and these compliance problems contribute to the development of drug resistant mycobacterial strains.
Clearly effective therapeutic regimens that include improved vaccination and treatment protocols are needed. A therapeutic vaccine that would prevent the onset of tuberculosis, and therefore eliminate the need for therapy is desirable. Although currently available therapeutic measures are effective, the emergence of drug resistant strains has necessitated new formulations and compositions that are more versatile than current drugs. What is needed are new anti-tubercular drugs that provide highly effective treatment, and shorten and simplify tuberculosis chemotherapy.
The present invention also relates to methods and compositions having improved anti-mycobacterial activity, namely compositions comprising novel β-carboline.
The present invention relates to novel β-carboline analogs, their preparation, and their use as pharmaceuticals and pharmaceutical compositions containing them.
More particularly the invention provides a compound of formula 10,12-diheptanoyl-11-hydroxy-3-methyl-β-carboline (Compound I) in freebase or acid addition salt form.
Compound I
FIG. 1
The reaction can be effected according to known methods, e.g., Friedels-Craft reaction wherein the known alkaloid harmine is acylated under different conditions to yield Compound I. Working up the reaction mixtures according to the above process and purification of the compounds thus obtained may be carried out in accordance to known procedures.
Acid addition salts may be produced from the free bases in known manner and vice-versa.
Compound I and its pharmaceutically acceptable acid addition salts, hereinafter referred to as agents of the invention, exhibit valuable pharmacological properties when tested in vitro using tuberculosis agent, and in level I and level II assay of toxicity using mammalian VERO cells lines, and are therefore useful as pharmaceuticals.
In particular the agent of the invention show high activity against tuberculosis organism. The agent of the invention are therefore useful for treatment of tuberculosis.
The agents of the invention may be administered in free form or in pharmaceutically acceptable salt form. Such salts may be prepared in conventional manner and exhibit the same order of activity as the free compounds.
Accordingly in a further aspect the present invention provides the agents of the invention for use as pharmaceuticals, more specifically for treatment in the above-mentioned conditions, e.g., tuberculosis.
The present invention furthermore provides a pharmaceutical composition comprising an agent of the invention in association with at least one pharmaceutically acceptable diluent or carrier. Such compositions may be formulated in conventional manner.
Agents of the invention may be administered by any conventional route, for example parenterally e.g. in form of injectable solutions or suspensions, or enterally, preferably orally, e.g., in the form of tablets or capsules.
The agents of the invention may alternatively be administered e.g. topically in the form of a cream, gel or the like, or by inhalation, e.g., in dry powder form.
Examples for compositions comprising an agent of the invention include, e.g., a solid dispersion, an aqueous solution, e.g. containing a solubilizing agent, a microemulsion and a suspension of an agent of the invention. The composition may be buffered to a pH in the range of e.g., from 3.5 to 9.5, by a suitable buffer.
The agents of the invention can be administered either alone or in combination with other pharmaceutical agents effective in the treatment of conditions mentioned above.
Thus, the agents of the invention can be used for the treatment of tuberculosis in combination with: ethambutol, isoniazid, pyrazinamide, rifampicin, streptomycin, ciprofloxacin, norfloxacin and p-aminosalicylic acid.
The pharmaceutical compositions for separate administration of the combination partners and for the administration in a fixed combination, i.e., a single galenical composition comprising at least two combination partners according to the invention, can be prepared in a manner known per se and are thus suitable for enteral, such as oral or rectal, and parenteral administration to mammals, including man, comprising a therapeutically effective amount of at least one pharmacologically active combination partner alone or in combination with one or more pharmaceutically acceptable carriers, especially suitable for enteral or parenteral application.
In particular, a therapeutically effective amount of each of the combination partners may be administered simultaneously or sequentially and in any order, and the components may be administered separately or as fixed combination.
Accordingly the invention also provides a combination comprising a therapeutically effective amount of an agent of the invention and a second drug substance, said second drug substance being for example for use in any of the particular indications hereinbefore set forth.
The preferred indications are treatment of tuberculosis.
The preferred agent of the invention for the above-mentioned indications is 10,12-diheptanoyl-11-hydroxy-3-methyl-β-carboline
In accordance with the foregoing, the present invention also provides the use of an agent of the invention as a pharmaceutical, e.g., for the treatment of tuberculosis.
Moreover the present invention provides the use of an agent of the invention for the manufacture of a medicament for the treatment of any condition mentioned above, e.g., tuberculosis.
The following examples illustrate the invention.